1. Technical Field
The present invention relates to an organic EL device and a process of producing the same.
2. Related Art
Light-emitting elements such as an organic light-emitting diode (hereinafter, referred to as “OLED”), which is called an organic EL (electroluminescent) element, a light-emitting polymer element, or the like, generally have a structure in which a light-emitting layer formed of, for example, an organic EL material is disposed between two electrodes. For example, JP-A-2004-311403 discloses a light-emitting element configured of a reflective electrode disposed on a substrate, a light-emitting layer disposed on the electrode, a reduction layer disposed on the light-emitting layer, and a transparent electrically conductive film disposed on the reduction layer.
The reduction layer in JP-A-2004-311403 enhances the injection of electrons to the light-emitting layer and is composed of a metal compound layer disposed on the light-emitting layer and a reducing metal layer disposed on the metal compound layer. In JP-A-2004-311403, the metal compound layer is made of lithium fluoride, and the reducing metal layer is made of aluminum. The lithium fluoride is reduced by the aluminum to simple lithium (3LiF+Al→3Li+AlF3). The simple lithium is doped on the light-emitting layer. This enhances the injection of electrons to the light-emitting layer.
The light-emitting element in JP-A-2004-311403 is utilized in a top-emission light-emitting device. The reducing metal layer formed of a simple metal such as aluminum desirably has a minimized thickness for efficiently extracting light emitted by the light-emitting layer to the observing side. However, when the thickness of the reducing metal layer is not larger than a predetermined level, the metal atoms aggregate into island-like shapes to form a discontinuous film. This causes problems of deterioration in the electrical conductivity and optical characteristics of the light-emitting device.